Thermionic tube



Aug 16, 1932- T. R. GOLDSBOROUGH THERMIONIC TUBE Filed March 27, 1928INVENTOR fiwwf TTORNEY Patented Aug. 16, 1932 UNi'l'ED STATES PATENTOFFICE TEADDE'US R. GOLDSBOROUGH, OF FOREST HILLS, PENNSYLVANIA,ASSIGNOB TO WEST- INGHOUSE ELECTRIC & MANUFACTURING COMPANY, ACORPORATION 01E PENN- SYLVANIA THERMIONIC TUBE Application filed March27, 1928. Serial No. 265,017.

My invention relates to thermionic devices, and it has particularrelation to thermionic amplifier tubes of the equipotential-cathode ypIn the patent to Nicolson, No. 1,459,412 is disclosed a thermionic tubehaving an equipotential cathode comprising an insulating ody coated withelectron-emissive oxides and provided with an internal heating elementfor raisin the oxides to the temperature at which they comethermionically active. Although the patent discloses the use of abattery for supplying potential to the cathode-heating element, it isnow customary in the art to utilize alternating current for thispurpose, reliance being placed on the thermal lag in the insulating bodyto prevent the presence of hum in the output of the tube.

Anode, or plate, potential for tubes of the type to which my inventionpertains is usually supplied either from batteries, or from a separatesource of rectified alternating current, when such tubes are utilized inradioreceiving apparatus. The use of batteries, or separate rectifiers,while satisfactory in situations where their weight is notobjectionable, is not advisable in airplane receivers or transmitters,however, nor in any other situation where both space and weight must beeconomized.

It is, accordingly, one object of my invention to provide a thermionicdevice which shall require neither batteries nor auxiliary rectifiersfor the supply of operating energy thereto.

Another object of my invention is to provide a combined thermionicamplifier tube and rectifier that shall be capable of being entirelyenergized from a source of commercial, or other, frequency alternatingcurrent.

Another object of my invention is to provide a combined thermionicamplifier tube and rectifier that shall have incorporated therein meansfor shielding the amplifier portion thereof from magnetic effectsproduced by the rectifier portion.

Another object of my invention is to provide a combined thermionicamplifier tube and rectifier that shall utilize a single heating elementfor both the amplifier portion and the rectifier portion thereof.

Another object of my invention is to provide, in a combined thermionicamplifier tube and rectifier, a rectifier portionthat :hall utilize acathode of the equipotential Another object of my invention is toprovide in a combined thermionic amplifier tube and rectifier, means forcontrolling the rectifying action of the rectifier portion thereof.

Another object of my invention is to provide a device of theaforementioned type that shall be capable of being utilized as agenerator of osc1llations at any desired frequency. as an amplifier, oras r dectector.

Another object of my invention is to pro vide a device of theaforementioned type that shall be capable of being entirely energizedfrom a source of alternating current of commercial, or other, frequency,without the manifestation of objectionable hum in the output circuitthereof.

Another, and more specific, object of my invention 'is to provide acircuit network of a novel type, particularly adapted to connect mycombined rectifier-amplifier to a source of alternating current.

A combined thermionic amplifier and rectifier device constructedaccording to 'my invention preferably comprises a single cathode-heatingelement for both the amplifier portion and the rectifier portionthereof. The cathode of the rectifier portion is so constructed andarranged that it, of itself, without other metallic elementsintervening, may serve as the anode for the amplifier portion of thedevice, and has the additional function of shielding the said amplifierportion from electromagnetic disturbance from the rectifier ortion.-

In ad ition, I have found it distinctly advanta eous, though notstrictly necessary, to provi e means for, in part, neutralizing thespace-char e in the rectifier portion. uch means pre erably takes theform of a grldelement interposed between the anodes and the cathodeconstituting the rectifier, in combination with means for impressing anydesired bias-potential thereon with reference to the said cathode.

The novel features that I consider characteristic of my invention areset forth wlth articularity in the appended claims. The inventionitself, however, both asto its organization and its method of operatlon,together with certain further objects and advantages thereof, will bestbe understood by reference to the following description of a specificembodiment, taken with the accompanying drawing.

The single figure of the drawing 1s a view in perspective of a preferredform of my combined amplifier-rectifier tube, certain of the elementsthereof being broken away to more clearly show the interior structure ofthe device, together with a diagrammatic view of the circuit networkIprefertoemploy for energizing the tube when it is utilized in radioreception.

The combined amplifier-rectifier tube comprises an evacuated glassenvelope 1 in whlch an elongated element 2, of porcelain, or the like,is axiall mounted. A plurality of openings 3 an 4 extend from end to endof the element 2, through which openings is threaded a loop 5 ofresistance wire. The loop 5 is provided with terminals 6 and 7 thatextend through the end of the envelope 1, and are connected respectivelyto the terminals of a seconda winding 8 of a power transformer 10. herimary winding 11 of the transformer may e energized from any convenientsource of alternating current.

A cylindrical metallic sheath 12, substantially coextensive with theelongated element 2, and having an enlarged bell-shape lower end 13, isfittedover the said element, and in close contact therewith for themajor portion of its length. The exterior surface of the upper ortion ofthe sheath 12 having the lesser iameter is coated with thermionicallactive oxides, and functions as a cathode wit. respect to a plurality ofcylindrical anodes 14 and 15 which encircle it.

The anodes 14 and 15 are provided with terminals 16 and 17,respectively, which extend through the end of the envelope and areconnected to the terminals of a secondary high potential, winding 18carried by the power transformer 10.

A grid, or space-charge-controlling, element 20 is disposed intermediatethe oxide-coated upper portion of the metallic sheath and the .onicallyactive oxides.

anodes 14 and 15, and is provided with terminal 21 which extends throughthe en unctions to lower the internal impedance of the rectifier portionof the device.

Although the grid 20 is not essential to the operativeness of mycombined amplifierrectifier, it is decidedly advantageous.

A relatively short metallic sheath 24 is disposed around the lower endof the heater element 2 adjacent to the enlarged portion 13 of the longmetallic sheath 12, which sheath 24 also carries an exterior coating oftheremi- The short sheath may, if desirable, be replaced by a metallicfilm electro-plated on the element 2, or by any other conductive coatingin good thermal contact with the said element' A grid 25 is disposedaround the short sheath 24, intermediate it and the enlarged portion 13of the long sheath 12, and has the usual function of the grid inthermionic amplifier tubes of well-known types.

The long sheath 12, the short sheath 24, and the grid 25 are providedwith terminals 26, 27, and'28, respectively, which extend through thelower end of envelope and are conductively connected to correspondingpins 30, 31 and 32 carried by a base member 33 into which the lower endof the envelope is cemented.

An input circuit is provided for the amplifier portion of the device,which circuit, if the device is to functon as a combined rectifier anddetector, comprises an inductor 34 having a tuning condenser 35connected in shunt thereto. One end of the inductor is connected througha grid leak 36 and grid condenser 37 to the pin 32, which pin, in turn,is electrically connected to the grid 25. The opposite end of theinductor is connected to the short sheath 24, which constitutes thecathode of the amplifier tube portion.

The input circuit may be coupled to a radiant energy receiving devicecomprising an antenna 38, a coupling inductor 40, and a groundconnection 41.

The output circuit of the amplifier tube portion of the device may betraced from the mtermediate point 23 of the secondary winding 18,through a conductor 42 to a filter circuit comprisin a plurality ofchoke coils 43, the primary winding 44 of an output transformer 45, andthen through a conductor 46 which is connected to the cathode 24. Eachof the choke coils has a bypass condenser 47 connected in shunt thereto,the said condensers having a common terminal which is conductivelyconnected to the pin 30 by way of a conductor 48 and consequently to theelongated sheath member 12.

The secondary winding of the output transformer 45 may be connected to afpair of telephones 50, as shown, or it ma orm the input circuit to asecond combine recti- I energized from the secondary winding 8 andserves to raise the upper end of the elongated sheath member 12 to sucha temperature that the oxide coating on the exterior surface thereofemits electrons. Y i

The electrodes 14 and 15, bein connected to o posite terminals of thehig potential win ing 18 constitute a full-wave rectifier with the upperor cathode, end of the sheath element 12. The space char e between thesaid electrodes and the oath e may be neutralized to a greater or lessextent b ad'usting the potential applied to the gri 20 rom the biasingsource 22. Ifthis potential is made sufliciently positive the impedanceof the rectifier (portion of the device may be considerably re uced. v

The rectified current, which will have a double-frequency component,flows down through the sheath member to the bell shape portion thereof,or to the se arate bell shape electrode if such an electro e isutilized, and from it across to the short sheath 24 which constitutesthe cathode for the amplifier portion of the device.

The grid 25 in the amplifier portion has the usual and well knownfunction of controlling the flow of space current between the anode andcathode. If, as shown, the device is utilized as a detector, the gridwill acquire negative charges dependent upon the size of the grid leakand grid condenser and u on the amplitude of the incoming signals. heoperation of the amplifier portion, therefore, differs in no way fromthe operation of other similar thermionic tubes.

The direct current com onent of the output current flows back to t emidpoint on the high potential secondary winding over the, pathpreviously traced, which path includes the primary winding of the out uttransformer. The cycle and 120 cyc e com onents of the current rectifiedin the recti er portion of the device are bypassed back to networkarranged for its ener ation the amount of hum in the output clrcuit ofthe m llifier portion thereof is substantially neggl e.

Although the device has been illustrated as applied to the detection ofincoming radiofr uency signals it may, of course, be utilize for theiramplification at radio frequencies instead, if desired.

By employin a cathode of the equipotential type inbot the rectifier andam lifier portions of my improved thermionic evice, and by providingsufiicient thermal-la in the insulating supporting elemelft '2 t roughwhich the heatlng wires extend, the hum re sulting from varying cathodetemperature is materially reduced.

In'addition, inasmuch as the lower end'of the long sheath 12 isinterposed between the rectifier and amplifier portions of the device,the said amplifier portion is effectively shielded against magneticdisturbances arising in the rectifierportion. The long sheath, oratleast the bell sha ed ortion thereof, should preferably be ma e o amagnetic material in order to more effectively serve as a screen.

Although I have illustrated and described a specific embodiment of myinvention, various modifications thereof and various modifications ofthe energizing circuits therefor will be apparent to those skilled inthe art. My invention is, therefore, not to be limited except insofar asis necessitated by the prior art or by the spirit of the appendedclaims.

I claim as my invention:

1. A unitary thermionic device comprising an evacuated envelope,elements constituting a rectifier and a radio valve, three of saidelements common to said rectifier and said valve, one of said threeelements constituting a heater unit and another of said three elementsconstituting an insulating member surrounding said heater unit.

2. A combined thermionic rectifier and am plifier comprising anevacuated envelope enclosing a heating element, a thermionically activeelementadapted to be heated by said heating element, a plurality ofelectrodes adapted to cooperate with said active element to constitute arectifier, and a second thermionically active element adapted tocooperate with said heating element and said first mentioned activeelement and with a control electrode to constitute a radio valve. 3. Acombined thermionic rectifier and amplifier comprising an evacuatedvessel enclosing a plurality of electrically distinct thermionicallyafiive elements, and a plurality of electrodes mounted to cooperate withone of said elements to constitute a rectifier therewith, thelast-mentioned element constituting an anode for the amplifier.

4. A combined thermionic rectifier and amplifier comprising a pluralityof complete triode units, means for shielding the amplifier unit fromthe rectifier unit, said scribed my name this 19th dag of March1928.

shielding means contituting an anode for said amplifier portion.

5. A combined thermionic rectifier and amplifier, including a pluralityof thermionicall active elements and a plurality of elect es, a heatingdevice common to said active elements, means adjacent one of said activeelements constituting a rectifier therewith, and means for conductingthe rectified current to the amplifier portion of the device saidlast-named means comprising a shield for preventing inductiveinterference between the rectifier and the amplifier portion.

Intestimony whereof, I have hereunto sub- THADDEUS R. GOLD BOROU

